Gas turbine engines contain a variety of seals to prevent the leakage of working medium air out of the main flowpath of the engine. Minimization of leakage is important since leakage degrades the efficiency of the engine thereby increasing the engine's fuel consumption and cost of operation. Moreover, pressurized air which escapes from the flowpath has an elevated temperature and may come in contact with engine components whose tolerance for such temperatures is limited.
Knife edge seals are commonly used to seal the annular gap between rotating and nonrotating coannular components in turbine engines. A knife edge seal is a ring of material extending radially from a nonrotating component toward a seal land on a neighboring, coannular rotating component (or from the rotating component toward the nonrotating component). The knife edge ring terminates in close proximity to the seal land to inhibit the leakage of air through the annular gap. During engine operation the knife edge ring can contact the rotating seal land due to imbalance of the rotating component, differential thermal response of the components, or imperfections in the concentricity or dimensions of the components. Such contact erodes the knife edge ring and the seal land and diminishes the effectiveness of the seal. Moreover, operational experience suggests that most of the seal degradation occurs quite early in the life of an engine. Accordingly, the engine operates with a deteriorated seal throughout much of its life.
The seal effectiveness can be restored by removing the engine from service, replacing or renovating the knife edge ring and renovating the seal land. Unfortunately this is time consuming and expensive and results in the loss of revenue while the engine is out of service. Furthermore, the renovated seal is no more durable than the original seal, therefore the need to replace or renovate the seal recurs periodically throughout the life of the engine.
What is needed is an effective, inexpensive and simple method for restoring the effectiveness of an intercomponent seal in a turbine engine. Ideally the restored seal is more durable than and at least as effective as the original seal.